Helmets and other protective clothing and related structures typically incorporate impact absorbing structures to desirably prevent and/or reduce the effect of collisions between the wearer and other stationary and/or moving objects. For example, an athletic helmet typically protects a skull and various other anatomical regions of the wearer from collisions with the ground, equipment, other players and/or other stationary and/or moving objects, while body pads and/or other protective clothing seeks to protect other anatomical regions. Helmets are typically designed with the primary goal of preventing traumatic skull fractures and other blunt trauma, while body pads and ballistic armors are primarily designed to cushion blows to other anatomical regions and/or prevent/resist body penetration by high velocity objects such as bullets and/or shell fragments.
A helmet or other protective headgear will typically include a hard or semi-hard, rounded shell with cushioning inside the shell, and typically also includes a retention system to maintain the helmet in contact with the wearer's head. When another object collides with the helmet, the rounded shape of the helmet desirably deflects at least some of the force tangentially, while the hard or semi-hard shell desirably protects against object penetration and/or distributes some amount of the impact forces over a wider area of the head. The impact absorbing structures between the helmet and the wearer's head (which typically contact both the inner surface of the helmet shell and an outer surface of the wearer's head) then transmit this impact force (at varying levels) to the wearer's head, which typically includes some level of deformation of the impact absorbing structures (as the impact forces are transferred therethrough) as well as potentially allowing direct contact between the hard shell and the head for extremely high impact forces.
A wide variety of impact absorbing structures have been utilized in protective garments and helmets over the millennia, including natural materials such as leathers, animal furs, fabrics and plant fibers. Impact absorbing structures have also commonly incorporated flexible membranes, bladders, balloons, bags, sacks and/or other structures containing air, other gases and/or fluids. In more recent decades, the advent of advanced polymers and foaming technologies has given rise to the use of artificial materials such as polymer foams as preferred cushion materials, with a wide variety of such materials to choose from, including ethyl vinyl acetate (EVA) foam, polyurethane (PU) foam, thermoplastic polyurethane (TPU) foam, lightweight foamed EVA, EVA-bound blends and a variety of proprietary foam blends and/or biodegradable foams, as well as open and/or closed cell configurations thereof.
The proper functioning of an item of protective headgear is often dependent upon the proper sizing and “fit” of the headgear to the wearer's head. A well-made but poorly fitting helmet will often not effectively protect the wearer's head from trauma and the effects of intense physical contact, as the proper sizing and fitting of a helmet to the wearer's head are typically necessary to optimize the helmet's ability to absorb and/or significantly ameliorate impacts. For example, a helmet that is too large for a wearer's head allows the user's head to move within the helmet, allowing the user's head to contact sides of the helmet during impact. Another major consideration in protective headgear is wearer comfort—if the helmet is uncomfortable or painful to wear, this discomfort may distract the user's attention (potentially leading to more severe impacts) and/or may cause the user to remove or displace the helmet prior to the moment of impact. Moreover, a helmet that is too small for the wearer's head may be uncomfortable or painful for the wearer to wear. While custom-made headgear can often be particularized and sized to an individual wearer's unique anatomy (with customization often accompanied by a hefty price tag), a less expensive mass-produced and distributed type of headgear will often be manufactured in a few standard sizes, with the closest available standard size selected for an individual wearer.
In many applications, helmets will have soft foam pads and/or inflatable liners on one or more interior surfaces that are designed to contact a wearer's head, bridging the gap between the inner helmet surface and the outer head surface and desirably providing a comfortable fit as well as helping protect the wearers' head from impact and/or injury. However, many existing designs and methodologies for selecting and sizing helmets and related interior pads/liners are cumbersome and generally ineffective in accommodating the unique shape and size of every wearer's head. Moreover, many helmet manufacturers may choose to use inexpensive and/or outdated protective technologies in the interior pads and liners, which in certain instances can greatly reduce the effectiveness of the helmet system and potentially lead to increased incidence and/or severity of injuries. In addition, conventional methods for selecting a helmet for a wearer may result in inaccurate sizing of the helmet for the wearer, allowing some movement of the wearer's head within the helmet and/or increased tightness of the helmet on the wearer's head. Accordingly, it may be desirable to maintain a number of different sizes of helmets and fitting elements, like liners and spacers, to accommodate a range of head sizes. However, maintaining an inventory of all of these differently sized elements can cause an undue burden, e.g., on a retail store or an equipment manager for a sports team.
Many football helmets are manufactured with inflatable comfort liners that may be sometimes combined with soft foam and/or other materials in an effort to help attenuate impact forces incident to the helmet. These inflatable liners can have a plurality of separate inflatable cells, with these cells adjacently arranged into a general shape inside the helmet, often with interconnect air passageways and the inflatable cells often include a separate valve-controlled inflation tube that may extend out the back or side of the helmet. To “fit” the helmet, the wearer or an assistant (often referred to as the “sizer”) may increase or decrease the pressure of air or other fluid/gas within the inflatable comfort liner to desirably increase and/or decrease the size of the cells, while seeking to improve the wearer's fit, comfort and protection. Unfortunately, inflatable liners and related technology often function sub-optimally, in that the inflatable cells are prone to leakage, damage and are highly sensitive to environmental temperatures (i.e., they commonly inflate and/or deflate due to temperature fluctuations and/or air pressure changes). Inflatable cells also require an increased frequency of adjustment (or “spot checks”) to maintain proper sizing in-between pressurization/depressurization cycles; they suffer from a lack of uniform inflation, where some portions of the inflatable comfort liner may be over-inflated and other portions under-inflated; and the inflatable cells are generally positioned on-top of the helmet, extending over the crown, notably causing a lift effect. Such negative characteristics of the inflatable comfort liners can adversely affect the fit of the helmet and reduce or eliminate any protection the helmet presumes to provide.
Conventional methods for sizing inflatable helmet liners to a wearer are generally cumbersome because the inflatable comfort liners of the helmet are typically integrated within the helmet, which requires the Sizer to undertake a number of steps to attain an optimal fitting of the helmet. For example, one conventional helmet sizing method requires that the Sizer (1) wrap a flexible or cloth measuring tape approximately 1″ above the wearer's eyebrows to measure the circumference of the wearer's head; (2) record the measurement, and compare the measurement to the helmet manufacturer's circumference chart to select the proper size, and if the measurement falls between helmet sizes, the smaller sized helmet should be sized first; (3) put the helmet into position on the wearer's head and properly inflate one or more air liner(s) inside the helmet (with such inflation occasionally requiring application of some lubrication); (4) moving the helmet on the wearer's head to test multi-axial movement of the helmet (to verify how tightly the helmet is fit and determine if independent helmet movement or slippage is allowed); (5) and then repetition of this process if unwanted movement is observed. The Sizer will then again repeat this process for each air liner in the helmet, and will also need to verify that the helmet's front edge is positioned a desired distance above the wearer's eyebrows to allow for proper visibility. This process must occur before each use of the helmet, and must also be repeated a number of times during the athletic activity, including after significant exertion by the wearer occurs, after each significant impact to the helmet, and after each time that the environmental air temperature and/or pressure changes significantly. In addition to the large number and frequency of these checks, manufacturers, retailers and equipment managers are often forced to stock a large number of helmet components and fitting elements, and are often obligated to use a wide variety of charts and inventory software to keep track of the large number of helmet sizing options to accommodate a range of head sizes. This causes an undue burden to all involved parties, including a need for maintaining an inventory of many differently sized helmets and/or elements as well as forcing equipment managers to carefully follow instructions and inspection checklists.
Conventional methods for properly sizing a helmet to a wearer are also typically inaccurate because they only measure the circumference of the head, which identifies the largest and/or widest cross-section of the wearer's skull, and these methods typically ignore any variations in the shape and/or surface features of the wearer's head. Such inaccurate measurements often lead to improperly fitted helmets, and improperly fitted helmets can lead to increased opportunity for head injuries. More specifically, improperly fitted helmets may transmit increased forces to the wearer's head, including rotational forces that may “overpower” the wearer's cervical muscles in their neck and head, and which may cause excessive damage to the brain.